The disclosure relates to an internal gear pump for a hydraulic vehicle brake system having the features of the disclosure. Internal gear pumps of this kind are used instead of conventionally used piston pumps in slip-controlled and/or power-operated vehicle brake systems and are often referred to, though not necessarily correctly, as return pumps.
Internal gear pumps are known. They have an annulus and a pinion, which is arranged eccentrically in the annulus and meshes over a segment of the circumference with the annulus. The annuluses are internally toothed gear wheels, the pinions are externally toothed gearwheels, and the annulus and the pinion can also be regarded as gearwheels of the internal gear pumps. The terms “pinion” and “annulus” are used to distinguish between them. Opposite the segment of the circumference over which the gearwheels mesh there is a crescent-shaped free space between the annulus and the pinion, which is here referred to as a pump space. Arranged in the pump space is a dividing element, on the outside and inside of which tooth tips of the two gearwheels rest and which divides the pump space into a suction space and a pressure space. Owing to its typical shape, the dividing element is often also referred to as a crescent or a crescent element. Another name for the dividing element is “filler piece”. When driven in rotation, the gearwheels pump fluid from the suction space into the pressure space. The prior art also includes internal gear pumps without a dividing element, and these can be referred to as gear ring pumps for the sake of distinguishing them.
One known method of laterally delimiting and sealing the pump space is to use axial disks, which are also referred to as control or pressure disks or plates. They are fixed against relative rotation and are acted upon in a pressure field by an outlet pressure of the internal gear pump. The pressure field is a typically crescent-shaped shallow recess on a side of the axial disk approximately covering the pressure space which is remote from the pinion and the annulus. To seal the pressure field, a pressure field seal is required, and there is generally a backing ring, which supports the pressure field seal from the outside against the outlet pressure of the internal gear pump prevailing therein.